People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Frequent nightmares or bouts of night terrors in childhood may be early indicators of psychotic experiences such as hallucinations, and interrupted thoughts in adolescence, possibly predicting mental health issues. Photo courtesy of Shutterstock.com.

The sound of heavy breathing, and cries for help from a child’s bedroom often derive from nightmares, or bouts of night terrors during sleep. Children may be scared of going to bed in fear that the “boogeyman,” or some other mythical creature will rise in the night and terrorize them in their sleep. Although doctors tell parents nightmares and night terrors are a normal part of childhood development, new research suggests it may be an early indicator of mental health issues. A study in the journal Sleep found the frequency of parasomnias such as nightmares, and night terrors, may foreshadow psychotic traits in adolescence.

Nightmares been considered to be a normal part of childhood development. A nightmare occurs during the deep stage of sleep — rapid eye movement (REM) — and results in feelings of terror, fear, distress, or extreme anxiety. “There are certain spiked signals that occur in the brain which are identified during this stage with an EEG (electroencephalogram),” Dr. Anandhi Narasimhan, child and adolescent psychiatrist in Los Angeles, Calif told Medical Daily. Late-night snacking before sleep can increase a person’s metabolism, and therefore, signal the brain to be more active.These dreams tend to occur in the later part of the night, and may often awaken the sleeper increasing the likelihood of recalling the dream. Nightmares do not generally signal unusual problems, as the majority of children between the ages of three or four, and seven or eight have them.

Similar to nightmares, night terrors also result in an increase in heart and breathing rate, and sweating, and result in intense crying and fear. However, night terrors occur during stage three of non-REM sleep due to over-arousal of the central nervous system that regulates brain activity during sleep. Sleep deprivation or feelings of stress can evoke these parasomnias.

A team of researchers at the University of Warwick in the U.K., believe susceptibility to psychosis could be due to the frequency of parasomnias during childhood. The researchers sought to investigate whether the duration and experience of specific parasomnia was linked to psychotic experiences in childhood. Data from the Avon Longitudinal Study of Parents and Children (ALSPAC), also known as the Children of the 90s birth cohort study based in South West England, was obtained to observe parasomnia and psychotic experiences in over 6,700 children between the ages of two and nine. The researchers relied on the reports about their children’s nightmares. Information about psychotic experiences such as delusions, hallucinations, and thought interference in the previous six months was elicited through semi-structured interviews with the children.

The findings revealed after analyzing the group of children six times between the ages of two and nine, children who had frequency of nightmares before age 12 were about four times more likely to have psychotic experiences during adolescence. Those who experienced night terrors in this group doubled the risk of these problems. The odds they would experience psychotic experiences during young adulthood increased with the incidence of nightmares. Children who had one period of persistent nightmares had a 16 percent risk, while those who reported three or more ongoing periods of nightmares during the study, had a 56 percent risk of psychotic experiences.

“Recurring nightmares in children typically indicate serious anxiety and psychological disturbance,” said Dr. Carole Lieberman, a psychiatrist in Beverly Hills, Calif to Medical Daily. She believes reoccurring nightmares can simply be a result of chaos in a child’s life such as parents getting divorced or a family member dying, but Lieberman says, “they could be early signs of an incipient psychosis.” Psychosis such as schizophrenia or manic depressive illness/bipolar disorder usually come from a child inheriting a genetic predisposition, and the psychotic symptoms could be triggered by the traumas in the child’s life.

Other doctors, like Dr. Mary Ann Block, medical director of the Block Center in Hurst, TX., believe reoccurring nightmares may signify a poor diet. “I find that most nightmares in children are from the release of epinephrine (adrenaline). Adrenaline if the fight or flight hormone. It is supposed to be released when we are in danger so that we can run fast or fight hard,” she told Medical Daily. When children engage in late-night snacking, they usually consume a lot of sugar or carbohydrates, which can result in hypoglycemia — low blood sugar. In response, the body releases adrenaline to raise the blood sugar, which makes the brain think the sleeper is in danger, and can cause a nightmare to occur as a result.

Whether nightmares, and or night terrors occur due to childhood traumas, or poor diets, the researchers of the study tell parents they shouldn’t worry. "We certainly don't want to worry parents with this news; three in every four children experience nightmares at this young age. However, nightmares over a prolonged period or bouts of night terrors that persist into adolescence can be an early indicator of something more significant in later life,” said Professor Dieter Wolke in the press release.

Parents are advised to promote healthy sleep hygiene behaviors in their children, and create an environment that allows them to get the best quality sleep. It’s recommended for children and adults to avoid sugary drinks before bed, and remove other distractions such as television from the bedroom. These tips are the most effective strategies for parents to minimize the reoccurrence of nightmares and night terrors in their children.